DIAGNOSIS The polycarbonate plastic of the container is porous and absorbs strong oils and odors. Normal dish soap and water won't cut it because it doesn't break down the oils that carry the smell.
FIX You need a deep clean. Here's the shop method: 1) Fill the container about halfway with warm water. 2) Add a generous drop of regular dish soap and a teaspoon of baking soda. 3) Put the lid on and run the blender on high for 30-60 seconds. 4) Dump that out, rinse thoroughly, and let it air dry completely with the lid off. The baking soda is a mild abrasive and a natural deodorizer that the blender's action forces into every micro-scratch.
IF THAT DIDN'T WORK For truly stubborn smells, use a vinegar solution. Fill the container 1/4 with white vinegar and 3/4 with warm water. Blend for 30 seconds, let it sit for 15 minutes, then rinse very well. The acetic acid in vinegar neutralizes the odor compounds.
HEADS UP Never put the container in the dishwasher. The high heat and harsh detergent can cloud the plastic and make it even more prone to absorbing smells and staining over time. Hand wash is the way to go.